Method and Apparatus for Cooling a Temperature-Sensitive Assembly of a Motor Vehicle

ABSTRACT

A cooling arrangement for cooling a temperature-sensitive assembly, (such as an electrical assembly) of a motor vehicle includes a condenser for liquefying at least a partial volume of a cooling medium in a cooling circuit, and an evaporator disposed downstream of the condenser on which the cooling medium can impinge and to which heat from the electrical assembly (12) can be applied. The cooling arrangement comprises a pump device by which the evaporator can be charged by at least the liquefied partial volume of the cooling medium. A method for cooling a temperature-sensitive assembly, such an electrical assembly, of a motor vehicle is also provided.

This application is a national stage of PCT International Application No. PCT/EP2009/001286, filed Feb. 24, 2009, which claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2008 019 816.1, filed Apr. 19, 2008 and No. 10 2008 035 216.0, filed Jul. 29, 2008, the entire disclosures of which are herein expressly incorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a cooling arrangement for cooling a temperature-sensitive assembly of a motor vehicle, having a condenser for liquefying at least a partial volume of a cooling medium in a cooling circuit and having an evaporator disposed downstream of the condenser to which the cooling medium can be flow and to which heat from the temperature-sensitive assembly can be supplied. The temperature-sensitive assembly may be, for example, an electric assembly.

Temperature-sensitive assemblies of a motor vehicle are those whose functionality can be affected at least temporarily by heating during operation of thee vehicle. Such heating may be a consequence of the operation of the assembly itself, or it may be attributable to an external heat input, for example an input of waste heat of a drive assembly or of solar radiation.

In particular in hybrid vehicles and/or electric vehicles, electric assemblies such as drive batteries, in particular lithium ion batteries, fuel cells and the like generate heat, wherein an amount of heat generated by the electric assembly depends on the load state of the electric assembly. Lithium ion batteries should however be operated in a temperature range of 20° C. to 30° C., in order to avoid that their lifespan reduces considerably.

For cooling the electric assembly, in particular the lithium ion battery, an evaporator can be arranged at the battery of a cooling plant designed for cooling a passenger cell of the motor vehicle. The electric assembly can be cooled by charging the evaporator with a cooling medium circulating in a cooling circuit of the cooling plant and by supplying heat of the electric assembly to the evaporator. The cooling plant for cooling the passenger cell of the motor vehicle hereby usually has a compressor for compressing the gaseous cooling medium, a condenser for liquefying at least a partial volume of the compressed cooling medium and an expansion member connected upstream of the evaporator for relaxing the compressed cooling medium.

Viewing an energy requirement of the cooling plant, the fact that the compressor of the cooling plant has to be operated even with cool ambient conditions, in which a cooling of the passenger cell of the motor vehicle by means of the cooling plant is not necessary, has hereby to be viewed in a disadvantageous manner, if heat shall be discharged from the electric assembly and supplied to the evaporator.

Alternatively, as described in German patent document DE 101 28 164 A1, a cooling medium circuit separate from the cooling circuit of the cooling plant can be provided for cooling the electric assembly. The cooling medium circuit can contain a brine as cooling medium, in particular a water-glysantine mixture. The cooling medium can be cooled by means of the cooling plant provided for cooling the passenger cell. The cooling medium is cooled by an evaporator, which is arranged in a cooling circuit of the cooling plant for cooling the passenger cell. The cooled cooling medium is supplied to the electric assembly via the separate cooling medium circuit.

With such a cooling arrangement, the fact that an inefficient heat transport chain is given during the cooling of the cooling medium in the separate cooling medium circuit, in particular when using the evaporator integrated in the cooling circuit of the cooling plant, has to be viewed as disadvantageous.

It is further known from the state of the art to cool the cooling medium of the separate cooling medium circuit, for example a water glycol mixture with ambient air at low ambient temperatures. When cooling of the separate cooling medium circuit by means of the ambient air of the motor vehicle, the cooler for cooling the cooling medium can be arranged in an air-hydraulically and thermally disadvantageous manner in the region of other coolers, for example provided for cooling an engine cooling medium or in a comparatively flow-technical disadvantageous manner in the lower floor region of the motor vehicle.

It is thus an object of the present invention to provide a cooling arrangement of the above-mentioned type, which cools of a temperature-sensitive assembly of a motor vehicle, particularly efficiently.

This and other objects and advantages are achieved by the cooling arrangement according to the invention for cooling a temperature-sensitive assembly, such as an electric assembly, of a motor vehicle, having a condenser for liquefying at least a partial volume of a cooling medium in a cooling circuit and having an evaporator arranged downstream of the condenser which can be charged with the cooling medium and to which can be supplied heat from the temperature-sensitive assembly. The cooling arrangement has a pump device by which the evaporator can be charged by at least the liquefied partial volume of the cooling medium.

The pump device is formed as a liquid pump that is designed for conveying the liquefied partial volume of the cooling medium. Compared to this, a compressor of the cooling circuit is designed for compressing and conveying of gaseous cooling medium, wherein an charging of the compressor with liquid cooling medium affects the functionality of the compressor.

The invention is based on the knowledge that in particular with temperatures of the ambient air of less than 20° C. of the temperature-sensitive assembly surrounding the motor vehicle can be discharged to the environment with a particularly low energy effort, namely only the energy effort necessary for operating the pump device. The pump device conveys to the evaporator at least the partial volume of the cooling medium liquefied by the condenser, whereby latent heat is withdrawn from the temperature-sensitive assembly, which heat has to be generated for transferring the liquefied cooling medium into a gaseous state. A particularly efficient cooling of the temperature-sensitive assembly, in particular the electric assembly, of the motor vehicle is thereby enabled.

Depending on the load conditions of the electric assembly, a cooling of the electric assembly can still be possible at ambient temperatures of up to 27° C., in particular by synchronized operation of the pump device, if the condenser is flown through by ambient air in a good manner, for example during a speedy drive of the motor vehicle.

It is hereby further advantageous that the condenser which can be arranged at an air-hydraulically particularly beneficial position of the motor vehicle, can be used for the particularly efficient discharge of heat of the temperature-sensitive assembly, in particular electric assembly. Compared to this, when cooling the temperature-sensitive assembly, in particular the electric assembly, by the separate cooling medium circuit known from the state of the art, the cooler for cooling the cooling medium is arranged in front of the condenser in an air-hydraulically and thermally disadvantageous manner or in a thermally and flow-technical disadvantageous manner, for example the lower floor of the motor vehicle, a wheel box or the like.

By omitting the separate cooling medium circuit, the cooling arrangement can be formed in a particularly compress and cost-efficient manner.

A particularly efficient cooling of the temperature-sensitive assembly, in particular electric assembly, is also enabled in that no heat transfer losses occur during a heat transfer between different heat transfer media, for example the cooling medium and the cooling medium.

Furthermore, lines of the cooling circuit, which supply the cooling medium to the temperature-sensitive assembly, in particular the electric assembly, can have a considerably lower cross section, than lines of the separate cooling medium circuit conveying the cooling medium.

The cooling of the temperature-sensitive assembly, in particular the electric assembly, furthermore effects largely isotherm conditions in the temperature-sensitive assembly by means of evaporating liquid cooling medium. This is because heating of the cooling medium during the direct cooling of the temperature-sensitive assembly by means of the evaporator only takes place if the cooling medium is completely evaporated. During the cooling of the temperature-sensitive assembly by means of a liquid cooling medium that does not evaporate, for example the water glycol mixture that can be used in the separate cooling medium circuit, the cooling mediums heats when flowing through the temperature-sensitive assembly. A less efficient cooling of the temperature-sensitive assembly is thereby given first and temperature differences of about 5° K can occur within the cooled temperature-sensitive assembly.

By the direct cooling of the temperature-sensitive assembly by means of the evaporating cooling medium, a cooling at higher ambient temperatures is thus possible than when using the separate cooling medium circuit.

In a particularly advantageous arrangement of the invention, the pump device, particularly formed as an immersion pump, is arranged at a collection device arranged in particular downstream of the condenser for collecting the liquefied partial volume of the cooling medium. The pump device thereby has a particularly good starting behavior. The pump device can hereby in particular formed integrated in the collection device, so that no additional disconnecting points have to be arranged in the cooling circuit additionally to those that have to be provided in any case.

It has furthermore been shown to be advantageous if the cooling circuit has a compressor for compressing the cooling medium downstream of the evaporator and upstream of the condenser, wherein an expansion element is connected upstream of the evaporator for relaxing the compressed cooling medium, and wherein a bridging device for bridging the compressor when charging the evaporator by means of the pump device is provided. It is thereby enabled to cool the temperature-sensitive assembly, even if comparatively high ambient temperatures are present, that is for example above 25° C., that is, if the temperature of the ambient air exceeds the temperature of the temperature-sensitive assembly. In this case, charging of the condenser with cooling medium compressed by means of the compressor is necessary for liquefying the cooling medium of the condenser.

The bridging device for bridging the compressor when charging the evaporator by means of the pump device can have a non-return valve in an advantageous manner, which can be flown through by the cooling medium when charging the evaporator by means of the pump device. A particularly simple, operating phase-dependent closing and/or opening of the bridging device is enabled thereby. When operating the compressor for charging the condenser with compressed coolant medium, the non-return valve closes the bridging device due to the pressure acting on the non-return valve.

It can be provided that the cooling medium can be charged with a pressure by means of the compressor, which pressure is higher than a maximum back pressure to be generated when flowing the cooling medium through the pump device. The compressor can thus effect a flow-through of the pump device acting as a non-return valve.

Complementarily or alternatively, a bridging device for bridging the pump device having in particular a non-return valve can be provided when charging the evaporator by means of the compressor. The cooling medium can thereby flow past the pump device in an unimpeded manner when operating the compressor. If the bridging device has a non-return valve, a forming of a short-circuit flow in the collection device when operating the pump device is additionally prevented.

It is further advantageous if a bypass device for bypassing the expansion element is provided that can be flown through by the cooling medium, which can be blocked by means of a first blocking device. At least the liquefied partial volume of the cooling medium can thereby be conveyed to the evaporator in a throttle-free, and thus especially efficient manner, by the pump device. A performance to be brought about by the pump device for conveying the liquefied partial volume of the cooling medium can be minimized thereby. The temperature-sensitive assembly can thus be cooled efficiently by means of the pump device with a compressor out of operation with an energy expenditure of less than 30 W, if the temperature of the ambient air of the motor vehicle falls below 20° C. A maximum temperature of the evaporator, which is supplied with heat from the electric assembly, is hereby about 30° C. An energy requirement of the motor vehicle for cooling the electric assembly is also particularly low.

In a further advantageous arrangement of the invention, a second blocking device is assigned to the expansion element, by which blocking device a flow-through of the expansion element is to be inhibited. It can be ensured thereby that the liquefied cooling medium flows to the evaporator in a throttle-free manner, when the pump device is operated.

The first blocking device and the second blocking device can for example be formed integrated into a three-way valve.

It is furthermore advantageous if the cooling circuit has a further evaporator for cooling a passenger cell of a motor vehicle, to which a further expansion element for relaxing the cooling medium compressed by a compressor is connected upstream. Thereby, the evaporator assigned to the temperature-sensitive assembly, and simultaneously the further evaporator, can be charged with the compressed cooling medium when operating of cooling circuit by means of the compressor, that is, with comparatively high ambient temperatures. The efficient cooling of the electric assembly is thus ensured on the one hand and a comfortable cooling of the passenger cell can simultaneously be achieved by the cooling circuit.

It has further been shown to be advantageous if a maximum difference between a pressure present upstream and downstream of the pump device can be adjusted by means of the pump device in the cooling circuit, wherein the further expansion element can be transferred to a closed position by means of this maximum difference. It can thereby be ensured with comparatively cool ambient temperatures, that is, if no cooling of the passenger cell is necessary, and only the temperature-sensitive assembly has to be cooled, that the liquefied partial volume of the cooling medium conveyed by the pump device is supplied to the evaporator, which is assigned to the temperature-sensitive assembly. The further expansion element can hereby for example be formed as a thermostatic expansion valve.

Complementarily, but preferably alternatively, a further blocking device can be assigned to the further expansion element, by which blocking device a flow-through of the further expansion element is to be inhibited.

In a further advantageous arrangement of the invention, the further expansion element can be transferred to an open position, in which the further expansion element can be flown through by the cooling medium in an essentially unimpeded manner. The further expansion element can hereby be formed as an electrically regulated expansion element, so that the liquefied coolant medium can be supplied to the evaporator for cooling the passenger cell in a throttle-free manner when charging the evaporator with the liquefied partial volume of the coolant medium.

This is in particular sensible if, for example with a circulating air operation, air flowing into the passenger cell is heated above the ambient temperature by an increased heat input. The heating can hereby be effected by operating an internal combustion engine of the motor vehicle, a fan motor and/or further electronic components. Furthermore, in particular the operating of an internal combustion engine and/or of an exhaust gas plant under a high load and/or high solar radiation can lead to a heating of the air flowing into the passenger cell. Hereby, temperatures can adjust in front of the further evaporator provided for cooling the passenger cell, which temperatures are clearly higher than 10° K above the ambient temperature of the motor vehicle.

By charging the further evaporator provided for cooing the passenger cell by means of the pump device, the air heated via the ambient temperature can be cooled in such a manner that air with a comfortable temperature flows into the passenger cell, without having to operate the compressor in the cooling circuit. If the compressor is operated when operating the internal combustion engine, a shutting down of the compressor brings about a fuel saving.

It has further been shown to be advantageous if the expansion element and the blocking devices or the expansion elements and the blocking devices are integrated in a charging module. Thereby, less disconnecting points have to be arranged in the cooling circuit than with a separate connection of the individual components in the cooling circuit. A susceptibility of the cooling circuit to leakages is thus reduced.

If an inner heat exchanger is connected upstream of the compressor, by which heat exchanger heat can be exchanged between the compressed cooling medium and the cooling medium exiting from the evaporator, the cooling circuit has a bridging device for bridging the inner heat exchanger in an advantageous manner when charging the evaporator that can be flown through, in particular bridging the expansion element. A difference of the temperature at the condenser and at the evaporator, which is assigned to the temperature-sensitive assembly for cooling, can thereby be used in a particularly extensive manner.

The preferred embodiments and advantages described for the cooling arrangement according to the invention are also valid for the method for cooling an electric assembly of a motor vehicle according to the invention.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of a cooling arrangement for cooling an electric assembly of a motor vehicle, wherein a cooling medium liquefied by a condenser is to be conveyed to an evaporator by a pump device, to which evaporator heat of the electric assembly can be supplied;

FIG. 2 is a pressure enthalpy diagram for illustrating a method for cooling the electric assembly by a compressor arranged in the cooling arrangement according to FIG. 1;

FIG. 3 is a pressure enthalpy diagram for illustrating a cooling process during the cooling the electric assembly by the pump device according to FIG. 1;

FIG. 4 shows a cooling arrangement for cooling the electric assembly and air in a climate box, via which the air can be supplied to a passenger cell of the motor vehicle according to a second embodiment; and

FIG. 5 shows a cooling arrangement for cooling the electric assembly according to a third embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a cooling arrangement 10 for cooling an electric assembly 12, which is shown as a lithium ion battery of a motor vehicle (not shown in detail). The electric assembly 12 can of course also be a fuel cell assembly or the like releasing heat under a load or as a temperature-sensitive assembly that can be heated due to an external heat input.

For cooling the electric assembly 12, an evaporator 14 is arranged thereon, which is included in a cooling circuit 16 of the cooling arrangement 10. In the cooling circuit 16 is further arranged a condenser 18, by which a cooling medium circulating in the cooling circuit can be liquefied.

A collection device 20 for collecting the cooling medium liquefied by means of the condenser 18 is arranged downstream of the condenser 18. A pump device 22 presently formed as an immersion pump is arranged in the collection arrangement and is designed for conveying liquefied cooling medium.

In particular with temperatures of less than 20° C., the cooling medium can be liquefied in the condenser 18 and be supplied to the condenser in the liquefied state. If a temperature of the evaporator 14 is above the ambient temperature, the liquid cooling medium can partially or completely evaporate in the evaporator 14, flow again to the condenser 18 and be liquefied there again at least partially. For evaporating the liquid cooling medium in the evaporator 14, the heat of the electric assembly 12 is hereby supplied to the evaporator 14 and the electric assembly is cooled correspondingly.

As can be seen in FIG. 1, a compressor 24 is connected upstream of the condenser 18 in the cooling circuit 16. When charging the evaporator 14 with liquefied cooling medium by means of the pump device 22, the cooling medium coming from the evaporator 14, which is at least partially evaporated, flows past the compressor 24 via a bridging device for bridging the compressor 24.

The bridging device 26 has a non-return valve 28 that can be flown through by the cooling medium when charging the evaporator 14 by the pump device 22. The non-return valve 28 and the bridging device 26 are presently formed integrated in the compressor 24. Thus, no further disconnecting points 30 have to be provided in the cooling circuit 16 due to the provision of the bridging device 26 with the non-return valve 28 than those that have to provided in any case when arranging the compressor 24. This is important in view of that an increase of a number of the disconnecting points 30, which are respectively indicated schematically in FIG. 1 upstream and downstream of the components of the cooling circuit 16, could lead to a higher leakage susceptibility of the cooling arrangement 10.

A non-return valve 32 arranged in the collection device 20 is arranged parallel to the pump device 22, so that the pump device 22 can be bridged when charging the evaporator 14 by the compressor 24.

The compressor 24 is presently consulted for charging the evaporator 14, if a difference between the ambient temperature and the temperature present at the evaporator 14 is not sufficient for cooling the electric assembly 12. In particular with temperatures of less than 20° C., a cooling of the electric assembly 12 by the evaporator 14 charged with liquid cooling medium by the pump 22 is however enabled.

When charging the evaporator 14 with cooling medium by the compressor 24, the compressed coolant medium liquefied in the condenser 18 is relaxed by means of an expansion element 34 connected upstream of the evaporator 14. The expansion element 34 can be formed as a fixed throttle.

So that the liquefied cooling medium can be supplied in a throttle-free manner to the evaporator 14 during the charging of the evaporator 14 with the liquefied cooling medium from the collection device 20 by the pump device 22, a first blocking device 36 in the cooling circuit 16 has to be opened, and a bypass device 38 for bypassing the expansion element 34 has to be freed thereby.

If however the evaporator 14 is to be charged with relaxed cooling medium, the compressor 24 is thus in operation, the bypass device 38 can be blocked by the first blocking device 36. A second blocking device 40, which is connected upstream of the expansion element 34, can be opened simultaneously.

The blocking devices 36, 40 and the expansion element 34 can of course be formed integrated into a charging module 42, whereby a number of disconnecting points can be kept low.

According to FIG. 1, the cooling circuit 16 has a further evaporator 44, which is provided for cooling a passenger cell of the motor vehicle. The further evaporator 44 is connected in parallel to the evaporator 14 in the cooling circuit 16 for cooling the electric assembly 12.

When operating the cooling arrangement 10 for cooling the electric arrangement 12, that is, with comparatively high ambient temperatures, the cooling medium circulates in the cooling circuit 16 due to the operation of the compressor 24.

According to FIG. 1, a further expansion element 46 is connected upstream of the further evaporator 44 for cooling the passenger cell of the motor vehicle, by which expansion element the cooling medium compressed by the compressor 24, liquefied in the condenser 18 can be relaxed. The further expansion element 46 can be formed as a therostatic expansion valve.

According to the embodiment of the cooling arrangement 10 shown in FIG. 1, a further blocking device 48 is connected upstream of the further expansion element 46, by which blocking device a flow-through of the further expansion element 46 is to be inhibited. The further expansion element 46 and the blocking device 48 connected upstream can of course also be formed integrated in the charging module. A number of disconnecting points 30 in the cooling circuit 16 is thereby reduced further.

A temperature sensor 50 is assigned to the expansion element 46 formed as a thermostatic expansion valve, by which sensor a temperature downstream of the further evaporator 44 can be sensed.

It can further be seen in FIG. 1 that a pressure sensor 52 is arranged between the condenser 18 and the collection device 20.

FIG. 1 further shows that an inner heat exchanger 54 is connected upstream of the compressor 24, by which heat exchanger heat can be exchanged between the compressed cooling medium and the cooling medium exiting the evaporators 14, 44. An efficiency of the cooling arrangement 10 is increased by the inner heat exchanger 54. Additionally it is ensured due to the inner heat exchanger 54 even when using the expansion element 34 formed as a cost-efficient fixed throttle connected upstream of the evaporator 14, that no liquid cooling medium is supplied to the compressor 24, even if the further evaporator 44 is not operated.

The blocking valve 48 connected upstream of the further expansion member 46 can be omitted, in particular if the further expansion element 46 designed for example as a thermostatic expansion valve expansion valve is in a closed position when a low pressure difference is present upstream and downstream of the pump device 22. Such a low pressure difference transferring the expansion element 46 into the closed position is presently given in the cooling circuit 16, if the evaporator 14 is charged by cooling medium by means of the pump device 22.

FIG. 2 shows a pressure enthalpy diagram, wherein a pressure p of the cooling medium in the cooling circuit 16 is logarithmically plotted on an ordinate, and an enthalpy h of the cooling medium on an abscissa.

A line curve 56 illustrates a state change of the cooling medium present in the cooling circuit according to FIG. 1 when cooling the electric assembly 12, wherein the compressor 24 is operated for charging the evaporator 14. In the pressure enthalpy diagram according to FIG. 2, a phase boundary line 58 is drawn additionally, which has an increasing course up to a peak 60, and a decreasing course behind the peak 60. The peak 60 simultaneously represents a critical point, so that supercritical relations are present when exceeding the pressure p assigned to the critical point.

At pressures p below the critical point, the cooling medium is present in the liquid state according to FIG. 2 with comparatively low enthalpy values. In a region 62 delimited to the top by the phase boundary line 58, a mixture of liquid and gaseous cooling medium is present. The cooling medium is completely present as a gaseous phase with relatively high enthalpy values of the cooling medium.

A corner point A of the line curve 56 describes a state of the cooling medium, in which it is present at the entry of the compressor 24 with a comparatively low pressure P and with a comparatively large enthalpy h. A corner point B illustrates the state of the gaseous cooling medium A compressed by the compressor 24.

In the condenser and in the inner heat exchanger 54 connected downstream thereof, the cooling medium under high pressure is liquefied in an isobaric manner. The liquefied state of the cooling medium is illustrated by the corner point C of the line curve 56 in FIG. 2. During relaxing by means of the expansion element 34 or 46, the pressure p of the cooling medium reduces by a pressure difference Δp, which has to be applied by the compressor 24 when compressing the cooling medium.

A temperature line curve given in FIG. 2 illustrates a temperature T_(U) of the ambient air. This is larger than a temperature T_(Batt) present at the electric assembly 12, which is depicted by a second temperature line 66 in FIG. 2.

In the evaporator 14 or 44 and in the inner heat exchanger 54, the coolant medium absorbs heat by evaporating the liquid phase, its enthalpy changes in an isobaric manner by an enthalpy difference Δh depicted in FIG. 2, which corresponds to a distance between the corner points D and A of the line curve 56. It can be seen in FIG. 2 that a comparatively high pressure changing work corresponding to the pressure difference Δp has to be used for discharging heat of the electric assembly 12, that is, for charging the cooling medium with the enthalpy difference Δh by means of the compressor 24.

FIG. 3 shows a line curve 68 in a pressure enthalpy diagram according to FIG. 2, which illustrates a state change of the cooling medium when charging the evaporator 14 by means of the pump device 22.

A temperature line 64 illustrating the temperature T_(U) of the ambient air is hereby arranged below the temperature line 66, the temperature T_(U) of the ambient air is thus lower than the temperature of the electric assembly 12 cooled by the evaporator 14. The corner point C of the line curve 68 illustrates the state of the liquid coolant medium present behind downstream of the condenser 18. A pressure of the liquid coolant medium becomes minimal by the pump device, increased by the pressure difference Δp given in FIG. 3, the corresponding state of the coolant medium is given by the corner point A.

When transferring the liquid cooling medium into gaseous cooling medium by heat absorption from the electric assembly 12 in the evaporator 14, the enthalpy h of the cooling medium changes by a comparatively large enthalpy difference Δh. The cooling medium present in a completely gaseous manner at the corner point B, that is downstream of the evaporator 14, is liquefied by means of the condenser 18, which is depicted in FIG. 3 by a line of the line curve 68 connecting the corner point B with the corner point C.

The line curve 68, as can be seen in FIG. 3, lies completely within a region delimited by the temperature line curves 64, 66. With state changes of the cooling medium within this region, the heat amount that can be withdrawn from the electric assembly 12 via the cooling medium, that is, the enthalpy difference Δh that can be transferred to the cooling medium is larger than the enthalpy difference Δh which is depicted in FIG. 2.

As can be seen in FIG. 3, evaporation and liquefying of the cooling medium during the direct cooling of the electric assembly 12 take place by the pump device 22 with the evaporator 44 charged with liquid cooling medium with virtually the same level of the pressure p.

FIG. 4 shows a further embodiment of a cooling arrangement 10, which essentially distinguishes itself from the cooling arrangement 10 shown in FIG. 1 in that a further expansion element 70 is connected upstream of the evaporator 44 that can be transferred into an open position by accessing it.

The alternative further expansion element 70 can be formed as an electrically controlled expansion valve, for example as a magnetic valve. In a closed position of the further expansion element 70, the further expansion element 70 serves as a blocking valve. In an open position that can be adjusted by the further expansion element 70, the further expansion element 70 can be flown through in a largely throttle-free manner.

This function of the transfer of the further expansion element 70 into the open position can be used if the air present in front of the further evaporator 44 has a higher temperature T_(L) than the temperature T_(U) of the ambient air. The air flowing to the further evaporator 44 in a climate box of the motor vehicle can for example be heated by heat input from an internal combustion engine operated in particular under a high load and/or exhaust plant and/or by waste heat of electric motors, electronic components and the like to temperatures of 5° K to 10° K above the temperature T_(U) of the ambient air. This heat introduction can again be increased by a circulating air operation and/or strong solar radiation.

In this case, the heated air in the climate box can be cooled to values just above the temperature T_(U) of the ambient air in that the pump device 22 charges the further evaporator 44 with liquefied cooling medium in a throttle-free manner. The compressor 24 is hereby not in operation. The passenger cell of the motor vehicle can thus be cooled very efficiently and in a fuel-saving manner by operating the pump device 22, if the temperature T_(U) of the ambient air is lower than the temperature T_(L) of the air in front of the further evaporator.

FIG. 5 shows a further embodiment of a cooling arrangement 10, which essentially corresponds to the embodiment of the cooling arrangement 10 shown in FIG. 1. In the cooling arrangement 10 according to FIG. 5 is however provided a bridging device 72 for bridging the inner heat exchanger 54.

The bridging devices 72 also bridges the expansion element 34 which can be formed as a fixed throttle, which is connected upstream of the evaporator 14. The non-return valve 32 arranged parallel to the pump device 22 in the collection device 20 according to FIG. 1 is arranged downstream of the expansion element 34 and upstream of an entry of the bridging device 72 in the charging module 42 according to FIG. 5.

The blocking device 40 assigned to the expansion element 34 is arranged downstream of the entry of the bridging device 72 in the charging module 42.

By bypassing the inner heat exchanger 54 via the bridging device 72, the low enthalpy h can be used particularly extensively in the liquefied coolant medium, in order to withdraw heat from the electric assembly 12 during evaporation in the evaporator 14.

The components connected upstream of the further evaporator 44, which components comprise the further expansion element 46 as expansion valve with the blocking device 48 connected upstream according to FIG. 5, can of course be formed integrated into the charging module 42.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 

1.-16. (canceled)
 17. A cooling arrangement for cooling a temperature-sensitive assembly of a motor vehicle, said cooling arrangement comprising: a condenser for liquefying at least a partial volume of a cooling medium in a cooling circuit; an evaporator disposed downstream of the condenser into which the cooling medium can flow, and to which heat of the temperature-sensitive assembly can be applied; and a pump device which causes at least the liquefied partial volume of the cooling medium to flow into the evaporator.
 18. The cooling arrangement according to claim 17, wherein the pump device is an immersion pump, arranged at a collection device which is downstream of the condenser, for collecting the liquefied partial volume of the cooling medium.
 19. The cooling arrangement according to claim 18, wherein: the cooling circuit has a compressor for compressing the cooling medium downstream of the evaporator and upstream of the condenser; an expansion element is connected upstream of the evaporator, for relaxing the compressed cooling medium; and a bridging device for bridging the compressor is provided during charging of the evaporator by the pump device.
 20. The cooling arrangement according to claim 19, wherein the bridging device has a non-return valve which can be flown through by the cooling medium when it flows into the evaporator via the pump device.
 21. The cooling arrangement according to claim 19, wherein the compressor applies pressure to the cooling medium, which pressure is larger than a maximum back pressure applied by the pump device during flow of the cooling medium through the pump device.
 22. The cooling arrangement according to claim 19, further comprising a bridging device having a non-return valve, for bridging the pump device when the evaporator is impinged on by the compressor.
 23. The cooling arrangement according to claim 19, further comprising: a bypass device for bypassing said expansion element, which bypass device can be flown through by the cooling medium; and a first blocking device for blocking said expansion element.
 24. The cooling arrangement according to claim 23, further comprising a second blocking device assigned to the expansion element, which blocking device is operable to inhibit a flow-through of the expansion element.
 25. The cooling arrangement according to claim 24, wherein the cooling circuit has a further evaporator for cooling a passenger compartment of the motor vehicle, and a further expansion element that is connected to the further evaporator upstream, for relaxing the cooling medium compressed by the compressor.
 26. The cooling arrangement according to claim 26, wherein: a maximum difference between a pressure present upstream and downstream of the pump device can be adjusted in the cooling circuit by the pump device; and the further expansion element can be moved to a closed position by this maximum difference.
 27. The cooling arrangement according to claim 25, wherein a further blocking device is assigned to the further expansion element, by which blocking device a flow-through of the further expansion element can be inhibited.
 28. The cooling arrangement according to claim 25, wherein the further expansion element can be moved to an open position, in which it can be flown through by the cooling medium in an essentially uninhibited manner.
 29. The cooling arrangement according to claim 24, wherein the expansion element and the blocking devices are integrated into a charging module.
 30. The cooling arrangement according to claim 19, wherein an inner heat exchanger is connected upstream of the compressor by which heat exchanger heat can be exchanged between the compressed cooling medium and the cooling medium exiting from the evaporator.
 31. The cooling arrangement according to claim 30, wherein the cooling circuit has a bridging device for bridging the inner heat exchanger that can be flown through by the pump device, when charging the evaporator.
 32. A method for cooling a temperature-sensitive assembly of a motor vehicle, wherein: at least a partial volume of a cooling medium in a cooling circuit can be liquefied by a condenser; an evaporator arranged downstream of the condenser is charged by the cooling medium; heat of the temperature-sensitive assembly is supplied to the evaporator; and the evaporator is charged by at least the liquefied partial volume of the cooling medium by a pump device. 